The world’s oceans have been experiencing enormous blooms of jellyfish, apparently caused by overfishing, declining water quality and rising sea temperatures. Now, scientists are trying to determine if these outbreaks could represent a “new normal” in whi
Among the spineless creatures of the world, the Nomura’s jellyfish is a monster to be reckoned with. It’s the size of a refrigerator — imagine a Frigidaire Gallery Premiere rather than a hotel minibar — and can exceed 450 pounds. For decades the hulking medusa was rarely encountered in its stomping grounds, the Sea of Japan. Only three times during the entire 20th century did numbers of the Nomura’s swell to such gigantic proportions that they seriously clogged fishing nets. Then something changed. Since 2002, the population has exploded six times. In 2005 the Sea of Japan brimmed with 20 billion jellyfish, hitting fisheries with 30 billion yen in losses.
Why has the Nomura’s jellyfish become a recurring nightmare? The answer could portend trouble for the world’s oceans. In recent years, populations of several jellyfish species have made inroads at the expense of their main competitor — fish — in a number of regions, including the Yellow Sea, the Gulf of Mexico, and the Black Sea. Overfishing and deteriorating coastal water quality are chief suspects in the rise of jellies. Global warming may be adding fuel to the fire by making more food available to jellyfish and opening up new habitat. Now, researchers fear, conditions are becoming so bad that some ecosystems could be approaching a tipping point in which jellyfish supplant fish.
Essential to thwarting any potential jellyfish takeover is a better understanding of the complicated dynamics between fish and jellyfish. Jellyfish are a normal element of marine ecosystems. Fish and jellyfish both compete for plankton. The predators keep each other in check: 124 kinds of fish species and 34 other species, including leatherback turtles, are known to dine on jellyfish, while jellies prey on fish eggs and, occasionally, on fish themselves. Juvenile fish of some species take refuge amid tentacles and eat jellyfish parasites. Fish and jellyfish “interact in complex ways,” says Kylie Pitt, an ecologist at Griffith University in Australia.
Overfishing can throw this complex relationship out of kilter. By removing a curb on jellyfish population growth, overfishing “opens up ecological space for jellyfish,” says Anthony Richardson, an ecologist at CSIRO Marine and Atmospheric Research in Cleveland, Australia. And as jellyfish flourish, he says, their predation on fish eggs takes a heavier toll on battered fish stocks.
“When an ecosystem is dominated by jellyfish, fish will mostly disappear,” says ecologist Sun Song, director of the Institute of Oceanology in Qingdao, China. “Once that happens, there is almost no method to deal with it.”
Total jelly domination would be like turning back the clock to the Precambrian world, more than 550 million years ago, when the ancestors of jellyfish ruled the seas.
Sun and others are racing to get a handle on the likelihood of such a marine meltdown coming true. Like their foe, the subject is slippery. It’s an enigma, for starters, why particular jellyfish run rampant. The troublemakers “are only a small fraction of the several thousand species of jellyfish out there,” says Richardson. These uber-jellies reproduce like mad, grow fast, eat most anything, and can withstand poor water quality. They are tough, Richardson says —“like cockroaches.”
The big question is whether these cockroaches of the sea are poised to hijack marine ecosystems. There’s anecdotal evidence that jellyfish blooms are becoming more frequent. But there are also cases in which jellyfish gained the upper hand on an ecosystem, only to suddenly relinquish it. For instance, biomass of Chrysaora jellyfish in the east Bering Sea rose sharply during the 1990s and peaked in 2000. Chrysaora then crashed and stabilized after 2001, apparently due to a combination of warmer sea temperatures and a rebound in numbers of walleye pollock, a competitor for zooplankton.
The jury is out on whether other jelly-blighted waters can regain ecological balance as quickly as the Bering Sea did. For that reason, says Pitt, no one can say for sure whether severe jellyfish blooms are a passing regional phenomenon or a global scourge requiring urgent measures to combat their spread.
Pitt is one of a small band of jellyfish researchers hoping to settle that question. With support from the National Center for Ecological Analysis and Synthesis in Santa Barbara, Calif., she and her colleagues on the center’s Jellyfish Working Group are gathering up datasets from around the world on jellyfish blooms. They expect to have a global picture — and be able to take the measure of their foe — in about a year, Pitt says.
Jellyfish clearly have an impact on human activity. Besides fouling fishing nets, they invade fish farms, block cooling intakes at coastal power plants, and force beach closures. Some jellies pose a mortal threat. Dozens of Jellyfish blooms can be caused by eutrophication, which can create dead zones around mouths of rivers.
Global warming may allow deadly jellyfish, now mostly found in tropical and subtropical waters, to conquer new turf in temperate waters as sea surface temperatures rise, warns Richardson. “It’s very likely that venomous jellyfish will move toward the poles,” he says.
The UK’S oldest environmental charity is to close because its income has been hit by cuts to local authority budgets. Environmental Protection UK, originally established in 1898 as the Coal Smoke Abatement Society, provides expertise, advice and analysis on air quality and land, waste and noise issues. It says it will stop functioning as a fully staffed and funded organisation in March 2012. However, it hopes that it can carry on with at least some of its work on a voluntary basis. Pressure from environmental groups has prompted US President Barack Obama to halt the progress of the Keystone XL Pipeline. If built, the pipeline would carry 700,000 barrels of crude oil a day from Canada’s Alberta oil sands to refineries along the U.S. Gulf of Mexico coast. The pipeline company, Transcanada, are not backing down, and plan to submit a new application for an alternate pipeline route.